Analytical apparatus for testing asphalts



July 24, 1934. H. G. NEVITT ANALYTICAL APPARATUS FOR TESTING ASPHALTSFiled 001;. 17, 1932 64am? 6 015w?! INVENTOR ATTORNEY SIG/VAL LIGHT)Patented July 24 1934 UNITED STATES PATENT OFFICE ANALYTICAL APPARATUSFOR TESTING ASPHALTS Henry G. Nevitt, Kansas City, Mo., assignor toWhite Eagle Oil Corporation, Kansas City, Mo., a corporation of DelawareApplication October 17, 1932, Serial No. 638,161

2 Claims. (01. 34-19) of specified penetration. To determine the perwcentage of this content it is necessary that the oils be reduced byevaporation to a residue of the desired consistency and the weightrelation 10 which this bears to the original sample be determined. Thisinvention has to do with an apparatus for performing the reduction byevaporation above outlined. It has more specifically to do withprovisions for handling the reduction in an automatic manner.

Asphalts are classified by their weight-percentage content of asphalticresidue of a specified consistency. This specified consistency isusually spoken of as, for example, 60 penetration asphalt and isdetermined by subjecting 'a sample of the residue at a certaintemperature to test under a needle of specified dimensions which isforced into the residue by a specified weight for a specified length oftime. "Other tests indicative 1 of the quality of the original materialare made upon the residue. One such .test is the ductility test whereina small formed sample of the residue terial insoluble in such solventsas carbon tetra chloride or carbon disulphide. The specified amount ofinsoluble residue in such tests is usually quite low. It may be seenfrom the nature of these tests that the manner in which the residue isproduced by evaporation from the original sample can be of muchinfluence upon the final outcome of the test. For instance, overheatingmay cause cracking of a portion of the residue exposed to suchoverheating, resulting in a destruction of valuable residual materialwith a corresponding thinning of the remainder by the lighter productsof cracking, resulting in a loss of penetration and ductility and alsothere may be from this cracking a deposit of carbon insoluble in thereagent used in testing.

Another variable in the manner of producing 0 the residue which mayaffect the test is that of oxidation. The exposure of the heated oilundergoing reduction to the atmosphere results in the oxidation of aportion cf it to materials of an asphaltic nature. In other words itcreates by 5 the very method of analysis some amount of a materialsimilar to that which the analysis is calculated to detect. The amountof oxidized material so made is small. It is to a great extentunavoidable, or at least economically unavoidable. It matters therefore,in order that independent workers may check each other, more that theoxidization shall be uniform from sample to sample and fromdetermination to determination than that it be avoided entirely.

Another variable which results in erroneous tests is the method of heatapplication, as a rapid rate of reduction will give results differingfrom a slower rate of reduction.

When the amount of the sample is small and the desired amount of residueunknown it is frequently impossible to reduce more than one sample. .Insuch cases it becomes necessary to remove the sample from the reductionapparatus several times and determine the consistency of the residue. Incase it is still too thin it must be again heated and reduced. Thiscooling and reheating may seriously affect the tests on the residue.Even when the desired amount of reduction is known it often becomesnecessary to remove, cool, weigh, and reheat the sample several times todetermine the exact point of stoppage unless this point is reached thefirst time by good fortune.

Present methods of performing this reduction vary. The most commonlyaccepted one is probably that set forth by the American Society forTesting Materials in their 1928 Book of Tentative Standards on pages528-532 and designated as Standard D 2431-28 T. A' short description ofthis apparatus to save reference is as follows:

A ring stand is used to support the setup which consists of ahemispherical dish for containing the sample to be reduced, placed in anair bath which is formed of sheet steel in the shape of a truncatedcone. The air bath is heated by an ordinary Bunsen burner. Suspendedabove the sample, with its bulb therein, is a thermometer of certainspecified characteristics. This method has several practical objections.The most annoying of these is probably that the container specified isquite unhandy for use in the regular penetration test. More vitaldefects are that due to the construction, the source of heat, if it is agas flame as is specified, can come in very direct contact with thesample container resulting in local overheating with its attendantirregular results in the determination. A second objection is that thesample being heated is exposed to the air in varying area and depth,allowing irregularities in oxidation. Other methods of per- 110 formingthe same reduction contemplate the use of sand baths or oil baths forthe heating medium. In a sand bath a considerable temperature differenceexists between the temperature to which the sample is exposed near thetop of the bath and the temperature to which it is exposed near thebottom of the bath with corresponding irregularities in the rate ofreduction. Further objection to sand baths lies in the fact that thesample container is in contact with a material of high specific heat andin case of poor control it is quite easy for it to become seriouslyoverheated. In the case of oil baths the material used in the bath mustnecessarily be an oil of high flash point. Such oils are also ofsumciently high specific heat to give trouble with the control of therate of heat. As a further defect they are quite tenacious and. can onlywith difiiculty be removed from the outside of the sample container whenit is removed for weighing. As a further difiiculty they have a creepingtendency and are apt to creep up and over the edge of the container orcontaminate the sample by condensation within the container of vaporsfrom the oil bath.

It will be noted from the above discussions that in addition to thevarious analyticaldefects of the various methods no one of them has anymethod by which the progress of the reduction may be observed other thanvisually. Due to the expansion of oils upon heating a visual method isextremely inaccurate. It has therefore been the object of this inventionto provide an apparatus for use in the reduction of asphaltic materialsto residues of specified consistency which will provide for a uniformmethod of treatment in orderthat variations from one determination toanother may be zed; to also provide a method in which the reduction maybe automatically stopped when a certain portion of the sample has beenevaporated, to provide an apparatus wherein the rate of heating may beso controlled as to be uniform throughout the determination, and toprovide a method whereby this analytical determination may be carriedout with a minimum of attention from the analyst.

The principle upon which this invention is based is thatvof placing thesample on one end of a balance arm which is so adjusted that when theweight of thesample has been reduced a specified amount the balance mayswing in the opposite direction which movement will result in removingthe sample from the zone of heat and which motion may be taken advantageof to out ed the supply of heat at the moment of movement.

To convert'an apparatus working on this basic principle into one ofcommercial characteristics requires a few accessory details. Thesedetails are explained in the description of the apparatus which follows:

In order that a commercial workable embodiment of the apparatus may beshown and that its details may be thoroughly made clear I have attacheda drawing which is hereby made a part of this specification. In thisdrawing Figure 1 shows a vertical elevation of the apparatus inoperating assembly, partially in section. Figure 2 shows a plan view ofa portion of the apparatus. Like numerals are used to designate the samepart throughout both figures. Figure 3 is a wiring diagram. In Figure 1,AMA designates a box or enclosure wherein the apparatus is set up. Thisenclosure may be made of sheet steel, "Iransite board or any similarmaterial, its function being solely to set off the area wherein the vdetermination is made from outside atmospheric disturbances. In orderthat the atmosphere within this enclosure may be changed to remove fumesand that it may be circulated to insure a constant temperaturethroughout the enclosure there is provided attached to the enclosure 9.fan B driven by a motor C or by other suitable means and communicatingwith the enclosure through a duct D. In order that the current of airfrom the fan may not play directly upon the apparatus for thedetermination a baflie E of the same material as the enclosure A isprovided. The enclosure with its fan, etc., may be of a size only largeenough to contain one reduction apparatus or it may contain a pluralityof such machines. Proper methods of releasing air from the enclosure tooutside atmosphere or to a stack 18 should be supplied. The apparatusproper consists of an electrical heater 1, the balance mechanism and anelectrical switch 2. The heater as shown is of a type in wide use inanalytical work in the oil industry and consists of a heating coil whichis exposed to the material being heated through an orifice in the topplate of the heater and a rheostat for controlling the amount of heat,which rheostat is adjusted by a knob at the bottom of the heater. Thisheater may be supported at the proper height in any convenient manner orthere may be substituted for it any other mannor of heating such as agas heater with proper air bath or sand bath although the preferredapparatus of my invention contemplates the use of an electric heatentoavoid the difficulties in herent in other metlfiids of heating. A shortdistance removed from the heater is a double support 3 of any convenientform presenting two upper'supporting-suriaces 4} of exactly the sameelevation upon which rests a knife edge 5. Attached to this knife edgeis a balance arm 6 arranged in such a manner that one of the extremitiesis above the orifice of the heating device. This end of the balance armis formed as a stirrup 7 which may be used to properly support a samplecup of specified dimensions 8. This sample cupis so held that it restsabove a metal cover plate 19 and is adjusted to allow about onequarterinch air space between plate and cup over'the orifice of the heater whenthis end of the beam is depressed. This adjustment is made by means ofstop 20. Extending upwardly from the stirrup 7 is a wire 9 which may beused to support a thermometer in of the proper type for use in thedetermination. Running under the balance beam and parallel to andattached thereto is a support arm 11. Slidably mounted upon this supportarm is a movable weight 12 with a thumb screw 13 by which its positionmay be fixed. The end of support arm 11 terminates in a threaded portion14 upon which end is mounted a weight 15. Adjustment of the positions ofweights l2 and 15 will accomplish balancing of the sample with a greatdegree of accuracy. Attached tothe end of beam 6 furthest removed fromthe heater is an arm 16 and mounted nearby within the enclosure is apressure switch 2 of such a nature that when its actuating member isdepressed by 16 the current flowing through the switch is cut off. It.may be seen from this description that a weighted sample can be placedin the cup 8 and the weights l2 and 15 so adjusted that when apredetermined portion of the sample has been evaporated the end of thebeam most remote from the heater will become heavier and therebydepressed, thus removing the cup 8 from the action of the heat andopening switch 2 through the action of arm 16. To render this actionmore definite and rapid once the system becomes unbalanced I haveconstructed beam 6 of a small piece ofangle iron open upward, though anyother form of channeled beam might be used. In the channel thus formed Ihave provided a steel ball 1'7 so mounted that it can roll back andforth, and stops at either end of the channel. As long as the weightrelations are such that the sample is heavier the ball will remain atthe position shown at the sample end of the beam. As soon as the weightsare altered and the sample rises the ball will immediately run to theother end of the beam giving a great discrepancy in weights and therebyefiecting a rapidly and definitely actuated functioning of the variousportions of the equipment.

Figure 3 is a wiring diagram showing how the heater and motor may bewired in parallel from a source of, power with snap switches to controleach circuit and the weight switch for controlling the operation of theheater. I have also found it convenient when using a plurality of thesemachines to install in some convenient place a signal light in thecircuit of each heater in order that the conditions of operation may besignaled to an analyst working some distance away.

In the use of this equipment the following details or procedure would befollowed. A container would be tared and the sample of oil weighed intoit and the combined weight of sample and container noted. From previousexperience or by estimate the necessary reduction of the sample would becalculated and a similar container placed in the weighing balance andfilled with fine sand, shot, or other material until its weight is thatwhichthe first container would have when its sample is reduced thedesired amount. This second container is then placed in the stirrup towater in sample to that point which is known from previous experience tomaintain the sample at a temperature of 480-5l3il" F. The apparatus canthen be left and receive no further attention. When the sample in thecontainer 8 has been reduced the desired percentage the beam 6, actuatedby weights 12 and 15 and assisted after initiation of movement byrolling ball 17 will act to remove the sample from the regionof heat toa region wherein it may cool, cut on? the current to the source of heat,and extinguish the signal light to notify the analyst that the reductionhas been completed. After a suitable time for cooling the sample maythen be removed to water bath for temperature equalization and itsconsistency and other properties noted. In accord= ance with the usualmethods several samples may be run to varying percentage of reduction,the consistency of each reduced sample noted and the percentage ofreduction required to gain a given consistency graphically interpolated.

As an. example of the operation of this machine in the examination of anasphaltic material which is to be analyzed for its content of asphalt ofa specified consistency I wish to present the following: It is knownthat the asphalt contains approximately 70% by weight of this residue ofspecified consistency so three samples are weighed out and one sample isreduced to say residue, one to and one to residue after the methodoutlined in the general matter of this specification. The consistency ofeach at these residues by the standard penetration test is noted and acurve is drawn plotting consistency against per cent residue. From thiscurve the percent residue having the standard consistency may bedetermined without actually evaporatingto that exact consistency. Thismethod is in nowise different from that at present employed except thatthe use of this apparatus enables a greater standardization of theconditions of heat application in degree and length of time therebybringing about a greater consistency of results and a greater exactitudeof analytical determination. It may thus be seen that I have provided anapparatus capable of controlling all of the variables in this particularanalytical determination. I have further provided an apparatus capableof conducting thereduction to a specified predetermined extent and thenautomatically stopping itself and removing the sample from the region ofalteration. As a result of these provisions I have not only increasedthe possibility of accuracy in the determination but I have renderedpossible great savings in time and attention. The amount and extent ofchange will be readily apparent to any one familiar with the analyticalprocedure at present used.

It is obvious that numerous other mechanical embodiments of thisinvention might be made without departing from the spirit of theinvention and I therefore wish to claim this invention in its widestequivalents except as limited within the following claims:

I claim:

1. In an analytical apparatus for the reduction of asphaltic oil samplesto a predetermined percentage of residue an enclosure, pressureventilating means for such enclosure, and within such enclosure anevaporating device, comprising a source of heat, a support, a balancearm mounted upon said support adjacent said heat source, one end of saidarm positioned above said source of heat, this end of said arm beingformed to provide a frame wherein a sample cup may be positioned abovethe source of heat, the weight of the unreduced sample and cup acting tocompel approach of the sample to the heat source, stop means whereby thesample cup approach may be limited to avoid contact with the heatsource, a weight upon the end of said arm remote from the heat source,said weight being adjustable in position to permit it to overbalance thesample when a predetermined amounthasbeen evaporated there-' from andthereby to remove said sample from said source of heat upon evaporationof said predetermined amount, a channel or trough partially coextensivewith said balance arm, a weight free to move therein substantiallyparallel to the length of said arm, inactive when sample is beingheated, acting to accelerate movement of-the arm when sample isover-balanced, an electric circuit controlling said source of heat, aswitch in said circuit, and means whereby the sample raising motion ofthe arm wunicated to said switch causes shut ofi of said heat source.

2. an analytical apparatus for the reduction of an asphaltic oil sampleto a predetermined percentage of residuecomprising an enclosure,ventilating means to insure uniform circulation of air therethrough, ameans of heat supply, a container for sample and means to maintain suchsamplecontainer in the heating region but free from contact with thesource of heat until the r 15 predetermined reduction has been obtainedand thereafter to remove the sample to a region away

